1. Field of the Invention
The present invention relates to a steering control method for a motor vehicle with a differential.
2. Description of the Prior Art
There has been already developed and laid open in the official gazette of Japanese Patent Application Laid-open No. 95939/1989 a driving force distribution control apparatus for a four-wheel drive vehicle having a transfer capable of altering a torque distribution to front and rear wheels, and restricting means capable of altering restricting forces to the right and left driving wheels; comprising longitudinal acceleration detection means for detecting the longitudinal acceleration of the motor vehicle, lateral acceleration detection means for detecting the lateral acceleration of the motor vehicle, discrimination means for discriminating the running condition of the motor vehicle on the basis of the value of the longitudinal acceleration detected by the longitudinal acceleration detection means and the value of the lateral acceleration detected by the lateral acceleration detection means, and driving force control means for attaining the optimum controls of the quantities of the torque distribution based on the transfer and the restricting forces based on the restricting means in accordance with the discriminated result of the running condition discrimination means.
It is widely known that, when the restricting means is actuated in dependency on the lateral acceleration in the turning condition of the motor vehicle in a front differential as in a central differential and a rear differential, the traction performance of the motor vehicle can be enhanced without sacrificing the turning performance thereof. In actuality, however, when a difference is produced between the driving forces of the right and left wheels by the actuation of the restricting means, a steering force or a counter steering force changes largely due to the mass offset of a suspension, namely, the offset between the axis of a kingpin and the center of a wheel tire. This incurs, not only the problem that the steering feeling of a driver is worsened, but also the problem that the driver fails to manipulate the steering wheel of the motor vehicle as desired in an extreme case.